If ever there was a series done on an obviously small budget then it was Blake's 7. But the episodes were incredible as science fiction with each one being a story in its own right. All thanks to Terry Nation (creator of the Daleks in Dr Who) who penned all 13 scripts of the first series and several in the following three. And as you rightly state, the best ending of any series. Thanks for the memory jog, Duane.
It was actually in the early google-age - when watching one of the Lara Croft movies where the geek watches them on his monitor - that I rediscovered them and was able to find out the original name of the series.
Space 1999 was certainly legendary for it's cheesiness and absurdity. I'm not sure it will ever be topped.
Sadly, I didn't have TV during the 1960's so I didn't see any of that decade's shows until much later in syndication.
In terms of the cheesy 70's , I don't think it would be a complete listing without the animated Star Trek.
Then there was Blakes 7, also British. If I recall correctly, it had the best "never gonna be a sequel" ending of any series ever. All of the main cast members turned on each other killed each other in a final gun battle.
Hmmm, I never really thought of The Avengers or The Prisoner (which I watched with my dad) as being Science Fiction per se.
Something else has just popped into my mind... what was that one where two people (a man and a woman?) wandered into a hidden valley in the Himalayas or somewhere and came back having learned all sorts of mystic powers... Do you recall this one?
Well I'm sorry to say I'm batting 100% (can that be a cricket reference too?) on your list of shows/movies. You missed a few however-
Time Tunnel, The Prisoner, The Avengers, My Favorite Martian, The Outer Limits, The Invaders, One Step Beyond, The Outer Limits, It's About Time, UFO, 6 Million $ Man, Incredible Hulk, Mork and Mindy...
As to the cheesiest, it's a difficult call, but UFO is a close one to Space 1999. (Both British, right?). Of those from the US I'd pick Land of the Giants. They got lots of cheese miles from just a big pencil and eraser...